The grain model has shown to be an appropriate reaction engineering model for the carbothermal production of beta-sialon from kaolin when pelletized mixtures of kaolin and coal are used as starting materials. When pellet size is below 1 mm in diameter (spherical pellets) pore diffusion can be
neglected and the overall rate is controlled by the chemical reaction rate. Above this size, pore diffusion shows a significant influence. This holds for reaction temperatures of 1400°C. The apparent activation energy is about 400 kJ/mole.
When the CO partial pressure is kept below 0.05 atm., at 1400°C relatively simple reactor design calculations can be used. Under these conditions the formation of beta-sialon can be treated as an elementary reaction. In general at least two steps of the complex reaction scheme are rate determining. This means that in order to achieve a reliable model, these steps should be distinguished. Experimental procedures should be developed to enable elucidation and separate modelling of these steps.
|Title of host publication||Processing ceramics|
|Editors||G. With, de, R.A. Terpstra, R. Metselaar|
|Place of Publication||London|
|Publisher||Elsevier Applied Science Publishers|
|Publication status||Published - 1989|
|Name||Euro-ceramics : European Ceramic Society conference (ECerS) : proceedings|